I would not change capitalization to conform to some standard. You are quoting someone else: you should quote him as accurately as possible. The original writer may or may not have had a good reason for capitalizing in that way. I don't think it's your perogative to decide that he didn't.
Occasionally when quoting we change capitalization to make a sentence look right. When we do, we normally put the changed letter in square brackets as a clue to the reader that we have changed something. For example, suppose the original said:
While living in London, his brother always carried an umbrella.
You wish to quote that without the restrictive clause. You could write:
"[H]is brother always carried an umbrella," Mr Jones reported.
Even when there is something in a quote that is clearly and obviously an error, we do not simply change it. Usually we leave the error, and if we feel necessary to make clear that the error is in the original and not introduced by us when copying it, we put "[sic]".
To take the extreme: I think we would all agree that it would be flat wrong to deliberately change the meaning of a sentence being quoted because we disagree with what the original writer said. Like if we are quoting someone who said, "Stalin was a great leader", then no matter how much you or I do not like Stalin, we do not have the right to change the quote to "Stalin was a terrible leader". You certainly could say that you disagree with the person you are quoting, buy you don't have the right to change his quote.
Well, obviously changing "great" to "terrible" completely changes the meaning of the quote. But I think the same principle applies to lesser changes. Once you say that a change is so small that it doesn't matter ... what's the limit? Who decides? Best to say "never".
Changing capitalization is unlikely to change the meaning of a quote: clearly we're at the very low end here. Still, writers do sometimes intend capitalization to convey meaning. There might well be a difference in intent between, "Mr Jones was a great leader" and "Mr Jones was a Great Leader".
In the particular example you give, I don't see any significance. But maybe the writer did. Maybe it is just a detail of style. And maybe not. I wouldn't touch it.